I totally agree with you, the team isn't doing well in the league but they have somehow managed to keep a incredible record in the Europa league so far this season. Personally, I don't think the coach is a problem but it's the club that's the main problem to the club itself. With the way things are going for Manchester United I really don't think they will get their Spanish opponent in the Europa league Round of 16.
One way or another, MU could reach the quarter-finals or even the semi-finals because they are unlikely to meet a serious opponent in the earlier stages. This season the Europa League is not as strong as before, there are a lot of average teams that can get in including against MU. Though to be honest, given how MU plays inside the EPL I wouldn't be surprised if they lose to even a weak team
Real Sociedad is Manchester United opponent in the Round of 16 and for some reasons I doubt if they will be getting past the Spanish side. But let's say they do, they have Lyon on their side of the draws also they Lazio and Athletic Club. From this draws, they are likely to meet Lyon in the Quarter finals and Lazio or Athletic Club in the Semis. Do you really think this current Manchester United side can actually win and eliminate these teams?